Quantitative study of exciton-exciton polarization interaction in a strongly coupled semiconductor quantum well microcavity

The nonlinear optical responses of a strongly coupled exciton-photon system in a semiconductor microcavity structure under weak excitation can be explained by a weak exciton-exciton interaction due to the nonideal bosonic (weakly interacting bosons) nature of the excitons. The exciton-exciton interaction leads to an attractive interaction between excitons with opposite spin, and a repulsive interaction between excitons with the same spin and a phase space filling. Earlier, we have reported the ratio of these interaction energies from the polarization-sensitive degenerate four-wave mixing on a strongly coupled GaAs quantum well (QW) microcavity under weak excitation density. In order to quantitatively determine the exciton-exciton polarization interaction energy, we have proposed a pump-probe nonlinear polarization rotation scheme. In the paper, we report the quantitative measurement of the exciton-exciton polarization interaction energy in the above mentioned system under strict weak excitation density using the pump-probe nonlinear polarization rotation (PR) technique. In the technique, the change of polarization state of a weak linearly polarized probe due to the anisotropy induced by a strong, circularly polarized pump is monitored in reflection geometry.